Process for the preparation of s-vinyl phosphorodithioates



United States Patent 3,073,859 Patented Jan. 15, 1953 hire 3,073,859PROCESS FGR THE PREPARATION OF S-VENYL PHQSPHORODITHIOATES Philip .1.Pare, Yorktown Heights, N.Y.,. assignor to American Cyanamid Company,New York, N .Y., a corporation of Maine No Drawing. Filed Sept. 21,1961, Ser. No. 139,590

'7 Claims. ((11-260-461) The present invention relates to anovel'process for preparing S-viny1 phosphorodithioates represented bythe general formula:

in which R is a lower alkyl radical.

Phosphorothioate compounds prepared by the process of the presentinvention which have the general. grouping:

s li/ HzC=CH-SP find utility as pesticides, particularly as insecticidesand as valuable intermediates. Advantageously,.they are prepared byadmixing an inert organic solvent and 0,0- dialkyl phosphorodithioicacid having the representative structure:

nop-r -sn 0,0-dimethyl phosphorothioate, 0,0'diethyl phosphorothioate,0,0-di-n-propyl dithiophosphorothioate, 0,0-dibutyldithiophosphorothioate, 0,0-dipentyl dithiophosphorothioate, 0,0-dihexyldithiophosphorothfoate, 0,0-diheptyl dithiophosphorothioate,

and isomers thereof.

Illustrative free radical catalysts suitable for use herein are:

Di-tert-butyl peroxide, Benzoyl peroxide, Azobisisobutyronitrile,

and equivalents thereof.

Suitable inert solvents for the aforementioned reaction include:

Hexane Benzene Cyclohexane Xylene Dioxane Toluene EtherDimethylformamide and equivalents thereof.

The compounds prepared by the process of the present invention areactive insecticides and may be used as sprays in organic solvents, asemulsions in water or other non-solvents, or on solid carriers, such astalc, clays, diatomaceous earths and the like. Such amounts of 7 sure inthe system to reach 375 p.s.i.

I inert carrier may be incorporated as are customarily employed in theart. However, the active pesticidal compound is advantageously presentin amounts ranging from about 0.1% to about 5%, based on the weight ofthe inert carrier. The S-vinyl phosphorodithioate compounds may furtherreact with mercaptans, such as methyl mercaptan, ethyl mercaptan, phenylmercaptan, and the like, to form corresponding thioethers.

In order to facilitate a further understanding of the invention, thefollowing examples are presented primarily for purposes of illustratingmore specific details thereof. It is to be understood, however, that thescope of the invention is not to be deemed limited thereby, except asdefined in the claims. Unless otherwise noted, parts given are byweight.

EXAMPLE 1 Preparation of 0,0-Diethyl S-Vinyl Plzosphorodithioate Asuitable stainless steel rocking autoclave is charged with 98 parts ofdiethyl phosphorodithioic acid, 73 parts of benzene and 2 parts ofdi-tert-butyl peroxide. After sealing, the clave is purged withnitrogen, evacuated and pressured with 100 p.s.i. of acetylene gas. Theautoclave is rocked and heated to C. where addition acetylene gas ispressured in to allow a total pres- As reaction occurs and acetylene isabsorbed, further additions of acetylene are necessary over a two-hourperiod. Reaction terminates when no pressure variation is noted.Following reaction, the autoclave is cooled. Residual gases are vented.The crude product totaled 179 parts. After removal of the benzenesolvent, 64 parts of 0,0-diethyl S-vinyl phosphorodithiosate aredistilled over at a boiling point of 62-64 C./0.1 mm. Hg. The index ofrefraction of the distillate is 1.512 at 27 C. The recovery of productcorresponds to a 61% conversion of the start ing-acid.

Calculated for PS O C H C, 49.90; H, 5.94; S, 22.20; P, 10.73. P, 10.98.

EXAMPLE 2 Preparation of O,'O-Dimethyl S-Vinyl PhosphorodithioateRepeating Example 1 in every detail except that the clave is chargedwith 47 parts of distilled dimethyl phosphorodithioate acid, 35 parts ofbenzene and 1.0 part of di-t-butyl peroxide. After reaction as inExample 1, 89 parts of reaction product are recovered. 7.5 parts ofS-vinyl 0,0-dimethyl phosphorodithioate are distilled at a boiling pointof 62-63" C./0.7 mm. Hg. The refractive index of the product is 1.527 at27 C. The conversion of starting acid to vinyl ester is 35% and analyzesas follows:

Calculated for PS O C H in percent: C, 26.05; H, 4.92; I

S, 34.7. Found: C, 26.38; H, 5.20; S, 35.03.

EXAMPLE 3 Preparation of 0,0-Diisopropyl S-Vinyl PhosphorodithioateFound: C, 50.35; H, 6.20; S, 22.45;

3 EXAMPLE 4 Preparation of 0,0'-Diethyl S-Vinyl Phosphoradithioate Asuitable stainless steel rocking autoclave is charged with 40 parts ofdiethyl phosphorodithioic acid, 55 parts benzene and 1.0 part of benzoylperoxide. After sealing, the clave is purged with nitrogen, evacuatedand pressured with 100 p.s.i. of acetylene gas. The autoclave is rockedand heated to 95 C. where additional gas is pressured in to allow atotal pressure of 350 p.s.i. in the vessel. The temperature is held at95 C.-98 C. for a two hour reaction period. The clave is next cooled,vented of residual gases and emptied. After removal of the benzenesolvent, 0,0-diethyl S-vinyl phosphorodithioate is recovered in 20%yields.

EXAMPLE 5 Preparation of 0,0-Diethyl S-Vinyl Phosphorodithioate Theprocedure of Example 4 is followed in every material respect except thatthe autoclave is charged with 40 parts of diethyl phosphorodithioicacid, 55 parts of henzene and 2.5 parts of azobisisobutyronitrile. Thereaction is carried out at 80 C. for two hours at a total clave pressureof 350 p.s.i. The recovery of 0,0-diethy1 S- vinyl phosphorodithioatecorresponds to an 18% conversion of initial starting acid.

EXAMPLE 6 Repeating Example 1 in every material detail except that theclave is heated to 180 C., held at that temperature over a fifteenminuteperiod and then cooled to room temperature over a one hour period. A 28%yield of 0,0-diethyl S-vinyl phosphorodithioate based on starting acidis obtained.

EXAMPLE 7 As above stated, the compounds .of the present invention arehighly active and etfective insecticides. To demonstrate the markeddegree of insecticidal activity, each of the products of the aboveexamples are dissolved in a solvent therefor comprising 65 percentacetone and 35 percent water at a concentration of 0.1 percent based onthe weight of the compound. The solution is sprayed on Nasturtium aphidsand the results of the tests are presented in the table below.

4 TABLE I Compound: Percent kill 0,0-dimethyl S-vinyl phosphorodithioate100 0,0-diethyl S-vinyl phosphorodithioate 100 0,0-diisopropyl S-vinylphosphorodithioate 98 I claim: 1. A method for preparingphosphorodithioates represented by the general formula:

CHz=CH-Sl o R wherein R is a lower alkyl radical which comprises:reacting under superatmospheric pressure from about 100 p.s.i. to about500 p.s.i. and elevated temperature from about C. to about 250 C. insubstantially equimolar amounts of acetylene and an 0,0-dialkylphosphorodithioic acid of the structure:

Row-1 m where R is a lower alkyl radical, in the presence of a freeradical catalyst.

2. A process according to claim 1, in which the free radical catalyst isdi-tert-butyl peroxide.

3. A process according to claim 1, in which the free radical catalyst isbenzoyl peroxide.

4. A process according to claim 1, in which the free radical catalyst isazobisisobntyronitrile.

5. A process according to claim 1, in which the phosphorodithioic acidis 0,0-dimethyl phosphorodithioic acid.

6. A process according to claim 1, in which the phosphorodithioic acidis 0,0-diethyl phosphorodithioic acid.

7. A process according to claim 1, in which the phosphorodithioic acidis 0,0-diisopropyl phosphorodithioic acid.

References Cited in the file of this patent UNITED STATES PATENTS2,864,741 Diveley Dec. 16, 1958 2,912,450 McConnell et a1 Nov. 10, 19592,976,308 Bacon Mar. 21, 1961 OTHER REFERENCES Groggins: Unit Processesin Organic'Synthesis, 5th ed. (1958), McGraw-Hill Book Co., New York,pages 597, 824, 825.

1. A METHOD FOR PREPARING PHOSPHORODITHIOATES REPRESENTED BY THE GENERALFORMULA: